Bottom source/drain silicidation for vertical field-effect transistor (FET)

ABSTRACT

A method for manufacturing a semiconductor device includes forming a first active region on a semiconductor substrate, forming a semiconductor layer on the first active region, patterning the semiconductor layer into a plurality of fins extending from the first active region vertically with respect to the semiconductor substrate, wherein the first active region is located at bottom ends of the plurality of fins, forming a silicide layer on exposed portions of the first active region, forming an electrically conductive contact on the silicide region, forming a second active region on top ends of each of the plurality of fins, and forming a gate structure between the plurality of fins, wherein the gate structure is positioned over the first active region and under the second active region.

TECHNICAL FIELD

The field generally relates to semiconductor devices and methods ofmanufacturing same and, in particular, to an integration method andstructure including a silicide connection for a bottom source/drain of afield-effect transistor (FET).

BACKGROUND

Fin field-effect transistor (FinFET) devices include a transistorarchitecture that uses raised source-to-drain channel regions, referredto as fins. A FinFET device can be built on a semiconductor substrate,where a semiconductor material, such as silicon, is patterned into afin-like shape and functions as the channel of the transistor.

Known FinFET devices include fins with source/drain regions on lateralsides of the fins, so that current flows in a horizontal direction(e.g., parallel to a substrate) between source/drain regions at oppositeends of the fins in the horizontal direction. The known structures havetheir architectures limited by scaling plateaus. For example, knownhorizontal devices can have contacted poly pitch (CPP) plateaus between30 nm and 50 nm, and are driven by such competing considerations aselectrostatics, contact resistance (R_(contact)), and maximum voltage(V_(max)).

SUMMARY

According to an exemplary embodiment of the present invention, a methodfor manufacturing a semiconductor device includes forming a source/drainregion on a semiconductor substrate, forming a semiconductor layer onthe source/drain region, patterning the semiconductor layer into aplurality of fins extending from the source/drain region vertically withrespect to the semiconductor substrate, wherein the source/drain regionis located at bottom ends of the plurality of fins, forming a silicidelayer on exposed portions of the source/drain region, and forming anelectrically conductive contact on the silicide region.

According to an exemplary embodiment of the present invention, asemiconductor device includes a substrate, a source/drain region on thesubstrate, a plurality of fins extending from the source/drain regionvertically with respect to the substrate, wherein the source/drainregion is located at bottom ends of the plurality of fins, a silicidelayer on exposed portions of the source/drain region, and anelectrically conductive contact on the silicide region.

According to an exemplary embodiment of the present invention, a methodfor manufacturing a semiconductor device includes forming a first activeregion on a semiconductor substrate, forming a semiconductor layer onthe first active region, patterning the semiconductor layer into aplurality of fins extending from the first active region vertically withrespect to the semiconductor substrate, wherein the first active regionis located at bottom ends of the plurality of fins, forming a silicidelayer on exposed portions of the first active region, forming anelectrically conductive contact on the silicide region, forming a secondactive region on top ends of each of the plurality of fins, and forminga gate structure between the plurality of fins, wherein the gatestructure is positioned over the first active region and under thesecond active region.

These and other exemplary embodiments of the invention will be describedin or become apparent from the following detailed description ofexemplary embodiments, which is to be read in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described belowin more detail, with reference to the accompanying drawings, of which:

FIG. 1 is a cross-sectional view illustrating formation of doped andnon-doped semiconductor layers in a method for manufacturing asemiconductor device, according to an exemplary embodiment of thepresent invention.

FIG. 2 is a cross-sectional view illustrating fin and isolation regionformation in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating deposition of a protectiveconformal layer 130 in a method for manufacturing a semiconductordevice, according to an exemplary embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating removal of a portion ofthe protective conformal layer in a method for manufacturing asemiconductor device, according to an exemplary embodiment of thepresent invention.

FIG. 5 is a cross-sectional view illustrating silicidation of a dopedsemiconductor layer in a method for manufacturing a semiconductordevice, according to an exemplary embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating stripping of theprotective layer in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention.

FIG. 7 is a three-dimensional view of a semiconductor deviceillustrating an arrangement of fins including hardmasks stacked thereon,and a bottom source/drain region, according to an exemplary embodimentof the present invention.

FIG. 8 is a cross-sectional view illustrating deposition of dielectriclayers in a method for manufacturing a semiconductor device, accordingto an exemplary embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating removal of portions ofspacer dielectric layers in a method for manufacturing a semiconductordevice, according to an exemplary embodiment of the present invention.

FIG. 10 is a cross-sectional view illustrating removal of interlayerdielectric layers in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention.

FIG. 11 is a cross-sectional view illustrating deposition of dielectriclayers in a method for manufacturing a semiconductor device, accordingto an exemplary embodiment of the present invention.

FIG. 12 is a cross-sectional view illustrating removal of portions ofspacer dielectric layers in a method for manufacturing a semiconductordevice, according to an exemplary embodiment of the present invention.

FIG. 13 is a cross-sectional view illustrating deposition of a gatestructure in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention.

FIG. 14 is a cross-sectional view illustrating removal of part of thegate structure in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention.

FIG. 15 is a cross-sectional view illustrating formation of a mask forgate structure patterning in a method for manufacturing a semiconductordevice, according to an exemplary embodiment of the present invention.

FIG. 16 is a cross-sectional view illustrating gate structure patterningin a method for manufacturing a semiconductor device, according to anexemplary embodiment of the present invention.

FIG. 17 is a cross-sectional view illustrating deposition of dielectriclayers to encapsulate the remaining gate structure in a method formanufacturing a semiconductor device, according to an exemplaryembodiment of the present invention.

FIG. 18 is a cross-sectional view illustrating gate structure recessingin a method for manufacturing a semiconductor device, according to anexemplary embodiment of the present invention.

FIG. 19 is a cross-sectional view illustrating deposition of dielectricspacer layers in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention.

FIG. 20 is a cross-sectional view illustrating removal of portions ofspacer dielectric layers in a method for manufacturing a semiconductordevice, according to an exemplary embodiment of the present invention.

FIG. 21 is a cross-sectional view illustrating deposition of interlayerdielectric layers in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention.

FIG. 22 is a cross-sectional view illustrating planarization ofinterlayer dielectric layers in a method for manufacturing asemiconductor device, according to an exemplary embodiment of thepresent invention.

FIG. 23 is a cross-sectional view illustrating selective removal of thehardmask and portions of the dielectric layers in a method formanufacturing a semiconductor device, according to an exemplaryembodiment of the present invention.

FIG. 24 is a cross-sectional view illustrating removal of portions ofinterlayer dielectric layers in a method for manufacturing asemiconductor device, according to an exemplary embodiment of thepresent invention.

FIG. 25 is a cross-sectional view illustrating epitaxial growth of topsource/drain regions in a method for manufacturing a semiconductordevice, according to an exemplary embodiment of the present invention.

FIG. 26 is a cross-sectional view illustrating deposition of aninterlayer dielectric layer in a method for manufacturing asemiconductor device, according to an exemplary embodiment of thepresent invention.

FIG. 27 is a cross-sectional view illustrating formation of contactregions in a method for manufacturing a semiconductor device, accordingto an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

Exemplary embodiments of the invention will now be discussed in furtherdetail with regard to semiconductor devices and methods of manufacturingsame and, in particular, to an integration method and structureincluding a silicide connection for a bottom source/drain of afield-effect transistor (FET).

Embodiments of the present invention relate to vertical transportarchitecture FET devices including source/drain regions at ends of thefins on top and bottom sides of the fins so that current runs throughthe fins in a vertical direction (e.g., perpendicular to a substrate)from a bottom source/drain region to a top source/drain region. Verticaltransport architecture devices are designed to extend the product valueproposition beyond conventional plateaus and address the limitations ofhorizontal device architectures by, for example, decouplingelectrostatics and FET V_(max) from CPP, providing a FinFET-equivalentdensity at a larger CPP, by removing the Lgate as a pressure point.

Embodiments of the present invention provide a low resistance connectionto an active (RX) area, which functions as a bottom source/drain regionof the vertically conducting fins. Embodiments of the present inventionreduce the resistance of the doped source/drain region by silicidingthis region using, for example, cobalt silicide (CoSi_(x)) or tungstensilicide (WSi_(x)), which have high thermal stability. According to anembodiment, the silicide layer is encapsulated by a bottom spacer layerto protect the channel region from the silicide.

It is to be understood that the various layers and/or regions shown inthe accompanying drawings are not drawn to scale, and that one or morelayers and/or regions of a type commonly used in complementarymetal-oxide semiconductor (CMOS), fin field-effect transistor (FinFET),metal-oxide-semiconductor field-effect transistor (MOSFET) and/or othersemiconductor devices may not be explicitly shown in a given drawing.This does not imply that the layers and/or regions not explicitly shownare omitted from the actual devices. In addition, certain elements maybe left out of particular views for the sake of clarity and/orsimplicity when explanations are not necessarily focused on the omittedelements. Moreover, the same or similar reference numbers usedthroughout the drawings are used to denote the same or similar features,elements, or structures, and thus, a detailed explanation of the same orsimilar features, elements, or structures will not be repeated for eachof the drawings.

The semiconductor devices and methods for forming same in accordancewith embodiments of the present invention can be employed inapplications, hardware, and/or electronic systems. Suitable hardware andsystems for implementing embodiments of the invention may include, butare not limited to, personal computers, communication networks,electronic commerce systems, portable communications devices (e.g., celland smart phones), solid-state media storage devices, functionalcircuitry, etc. Systems and hardware incorporating the semiconductordevices are contemplated embodiments of the invention. Given theteachings of embodiments of the invention provided herein, one ofordinary skill in the art will be able to contemplate otherimplementations and applications of embodiments of the invention.

The embodiments of the present invention can be used in connection withsemiconductor devices that may require CMOSs, MOSFETs and/or FinFETs. Byway of non-limiting example, the semiconductor devices can include, butare not limited to CMOS, MOSFET and FinFET devices, and/or semiconductordevices that use CMOS, MOSFET and/or FinFET technology.

As used herein, “vertical” refers to a direction perpendicular to asubstrate in the cross-sectional and three-dimensional views herein.Current between source/drain regions is described herein as flowing in avertical direction (e.g., from a bottom source/drain region to a topsource/drain region) through a fin channel region.

As used herein, “horizontal” refers to a direction parallel to asubstrate in the cross-sectional and three-dimensional views herein.

As used herein, “thickness” refers to a size of an element (e.g., alayer, trench, hole, etc.) in the cross-sectional views measured from abottom surface to a top surface, or a left side surface to a right sidesurface of the element, and/or measured with respect to a surface onwhich the element is directly on.

Unless otherwise specified, as used herein, “height” or “height above asubstrate” refers to a vertical size of an element (e.g., a layer,trench, hole, etc.) in the cross-sectional views measured from a topsurface of the substrate 102 to a top surface of the element. Athickness of an element can be equal to a height of the element if theelement is directly on the substrate.

As used herein, “lateral,” “lateral side,” “lateral surface” refers to aside surface of an element (e.g., a layer, opening, etc.), such as aleft or right side surface in the cross-sectional views herein.

FIG. 1 is a cross-sectional view illustrating formation of doped andnon-doped semiconductor layers in a method for manufacturing asemiconductor device, according to an exemplary embodiment of thepresent invention.

A fin of a FinFET can include, for example, silicon, and is a conductingchannel that protrudes vertically from a substrate and conducts in adirection from a source to a drain. As can be understood by one ofordinary skill in the art, a plurality of fins can be formed on thesubstrate 102 and spaced apart from each other at regular intervals. Aplurality of gates can intersect the fins.

Referring to FIG. 1, a semiconductor substrate 102 can be, for example,a bulk substrate including semiconductor material including, but notlimited to, silicon (Si), silicon germanium (SiGe), strain-relaxedbuffer (SRB) SiGe, silicon carbide (SiC), silicon-germanium-carbon(SiGeC) or other like semiconductor. In addition, multiple layers of thesemiconductor materials can be used as the semiconductor material of thesubstrate.

In accordance with an embodiment of the present invention, as can beseen in FIG. 1, a n+ or p+ doped semiconductor layer 105 of and anon-doped semiconductor layer 110 are epitaxially grown. The dopedsemiconductor layer 105 can include, but is not limited to, Si, SiGe orSiC. The non-doped semiconductor layer 110, also referred to herein as achannel layer, can include, but is not limited to, Si, SiGe or III-Vmaterials. For purposes of explanation, the semiconductor layer 110 maybe referred to as a silicon layer.

Doping of the semiconductor layer 105 can be performed using, forexample, ion implantation, or annealing if not using an epitaxialprocess. In a non-limiting illustrative example, the doping of the layer105 uses, for example, arsenic (As) or phosphorous (P) for n-type device(e.g., nFET), and boron (B) for a p-type device (e.g., pFET), atconcentrations in the general range of e20/cm³.

Terms such as “epitaxial growth” and “epitaxially formed and/or grown”refer to the growth of a semiconductor material on a deposition surfaceof a semiconductor material, in which the semiconductor material beinggrown has the same crystalline characteristics as the semiconductormaterial of the deposition surface. In an epitaxial deposition process,the chemical reactants provided by the source gases are controlled andthe system parameters are set so that the depositing atoms arrive at thedeposition surface of the semiconductor substrate with sufficient energyto move around on the surface and orient themselves to the crystalarrangement of the atoms of the deposition surface. Therefore, anepitaxial semiconductor material has the same crystallinecharacteristics as the deposition surface on which it is formed. Forexample, an epitaxial semiconductor material deposited on a {100}crystal surface will take on a {100} orientation.

Examples of various epitaxial growth processes include, for example,rapid thermal chemical vapor deposition (RTCVD), low-energy plasmadeposition (LEPD), ultra-high vacuum chemical vapor deposition (UHVCVD),atmospheric pressure chemical vapor deposition (APCVD), liquid-phaseepitaxy (LPE), molecular beam epitaxy (MBE) and metal-organic chemicalvapor deposition (MOCVD). The temperature for an epitaxial growthprocess can range from, for example, 550° C. to 900° C., but is notnecessarily limited thereto, and may be conducted at higher or lowertemperatures as needed.

A number of different sources may be used for the epitaxial growth. Forexample, the sources may include precursor gas or gas mixture includingfor example, a silicon containing precursor gas (such as silane) and/ora germanium containing precursor gas (such as a germane). Carrier gaseslike hydrogen, nitrogen, helium and argon can be used.

FIG. 2 is a cross-sectional view illustrating fin and isolation regionformation in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention. Fins,such as fin 120, can be formed by patterning the semiconductor layer 110into the fins 110. A hardmask 125 including, for example, a dielectricmaterial, such as silicon nitride (SiN) is formed on portions that areto be formed into the fins 120. The fin patterning can be done by aspacer image transfer (SIT) process, for example. The SIT processincludes using lithography to form a pattern referred to as a mandrel.The mandrel material can include, but is not limited to, amorphoussilicon or amorphous carbon. After the mandrel formation, a conformalfilm can be deposited and then followed by an etchback. The conformalfilm will form spacers at both sides of the mandrel. The spacer materialcan include, but is not limited, oxide or SiN. After that, the mandrelcan be removed by reactive ion etching (ME) processes. As a result, thespacers will have half the pitch of the mandrel. In other words, thepattern is transferred from a lithography defined mandrel to spacers,where the pattern density is doubled. The spacer pattern can be used asthe hardmask 125 to form the fins 120 by RIE processes. According to anembodiment, the fins can be patterned to height to about 20 nm to about50 nm.

FIG. 2 also illustrates formation of isolation regions 115 in a methodfor manufacturing a semiconductor device, according to an exemplaryembodiment of the present invention. Portions of the substrate 102 anddoped semiconductor layer 105 are etched to form trenches in the layers102 and 105, in which a dielectric material, including, but not limitedto silicon dioxide (SiO₂), low-temperature oxide (LTO), high-temperatureoxide (HTO), flowable oxide (FOX) or some other dielectric, is depositedto form isolation regions 115, such as, for example, shallow trenchisolation (STI) regions. The dielectric material can be deposited usingdeposition techniques including, but not limited to, chemical vapordeposition (CVD), plasma enhanced CVD (PECVD), radio-frequency CVD(RFCVD), physical vapor deposition (PVD), atomic layer deposition (ALD),molecular layer deposition (MLD), molecular beam deposition (MBD),pulsed laser deposition (PLD), and/or liquid source misted chemicaldeposition (LSMCD), sputtering, and/or plating, followed by aplanarization process, such as, chemical mechanical planarization (CMP)to remove excess isolation material.

FIG. 3 is a cross-sectional view illustrating deposition of a protectiveconformal layer 130 in a method for manufacturing a semiconductordevice, according to an exemplary embodiment of the present invention.As shown in FIG. 3, a conformal deposition process, such as, forexample, ALD or MLD can be used to deposit conformal layer 130 on theisolation regions 115 and the semiconductor layer 105, and on and aroundthe fins 120 including the hardmasks 125 thereon. The layer 130 caninclude, but is not limited to, siliconborocarbonitride (SiBCN), siliconoxycarbonitride (SiOCN), SiN or SiO₂.

FIG. 4 is a cross-sectional view illustrating removal of a portion ofthe protective conformal layer 130 in a method for manufacturing asemiconductor device, according to an exemplary embodiment of thepresent invention. As shown in FIG. 4, the horizontal portions of thelayer 130 on the isolation regions 115, the semiconductor layer 105, andon top of hardmasks 125, are etched back to form spacer-like shapes toprotect the fins 120 during metal silicidation. The etch can be, forexample, an anisotropic etch, such as ME, ion beam etching, plasmaetching or laser ablation.

FIG. 5 is a cross-sectional view illustrating silicidation of the activesurface (i.e., doped semiconductor layer 105) in a method formanufacturing a semiconductor device, according to an exemplaryembodiment of the present invention. As shown in FIG. 5, according to anembodiment, the isolation regions are first recessed to a level belowthe layer 105, using, for example, an etching process, so that ends ofthe layer are exposed and can be covered with a deposited metal layer.Then, a metal layer including a material capable of forming a silicideis deposited on the layer 105 and the isolation regions 115. Thematerial can include, but is not limited to, metals such as cobalt andtungsten, or combinations thereof. The material preferably is thermallystable, being able to remain stable under high temperatures due tosubsequent steps performed under high temperature conditions. The metallayer can be deposited using deposition techniques including, but notlimited to, CVD, PECVD, RFCVD, PVD, ALD, MLD, MBD, PLD, and/or LSMCD,sputtering, and/or plating.

Then, a process, such as, for example, an annealing process atapproximately 300° C. to approximately 700°, is performed so that themetal layer reacts with silicon in the layer 105 to convert a portion ofthe layer 105 into a silicide layer 140. The annealing process is notnecessarily limited to the temperature range above, and may be performedat other temperatures if required. The silicide layer 140 may include,but is not limited to, cobalt silicide (CoSi_(x)), tungsten silicide(WSi_(x)) and combinations thereof. As shown in FIG. 5, due to thereaction with the layer 105, portions of the layer 105 are replaced bythe silicide layer 140. As can be seen, portions of the silicide layer140 wrap around left and right edges of the layer 105 to form an L-shapewhere the isolation regions 115 were recessed, and the metal layer wasable to react with the edges of the layer 105. The wrapping of the edgesof layer 105 by the silicide layer 140 further lowers resistance for theresulting bottom source/drain region.

The part of the metal layer formed on the isolation regions 115 prior tothe annealing step is removed by, for example, an etching process, suchas a wet etch, since those parts of the metal layer 140 do not reactwith the isolation regions 115, and are not converted to a silicideduring the annealing process.

FIG. 6 is a cross-sectional view illustrating stripping of theprotective layer in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention. As shownin FIG. 6, after silicidation, the protective layer 130 is stripped fromthe sides of the fins 120 and hardmasks 125 stacked on the fins 120. Thestripping can be performed using, for example, an H₄PO₃ solution forSiN, a hydrofluoric acid (HF) solution or NH₄/F based dry etching forSiO₂ and an isotropic dry etching process for SiBCN.

FIG. 7 is a three-dimensional view of a semiconductor deviceillustrating an arrangement of fins including hardmasks stacked thereon,and a bottom source/drain region, according to an exemplary embodimentof the present invention. Referring to FIG. 7, the fins 120 includinghardmasks 125 stacked thereon can form an nFET or a pFET depending ondoping of the bottom source/drain region (e.g., semiconductor layer105). As can be seen, as described further herein, contacts 203 (seeFIG. 27) conduct electrical current to the bottom source/drain regionsso that current can flow upward vertically through the fins 120 to topsource/drain regions (not shown). Although not shown in FIG. 7, thebottom source/drain regions 105 include the silicide layers 140 toreduce the resistance of the bottom source/drain regions. FIG. 7 furtherillustrates the isolation regions 115.

The following description in connection with FIGS. 8-10 illustrates aprocess flow for forming spacer layers, according to an exemplaryembodiment of the present invention, while FIGS. 11-12 illustrate analternative process flow for forming spacer layers, according to anexemplary embodiment of the present invention.

Following from FIG. 6, FIG. 8 is a cross-sectional view illustratingdeposition of dielectric layers in a method for manufacturing asemiconductor device, according to an exemplary embodiment of thepresent invention. As shown in FIG. 8, spacer dielectric layers 150,such as, for example a PECVD-type, high aspect ratio process (HARP)-typeor high density plasma (HDP)-type low-K dielectric layers, including,but not limited to, SiBCN, SiOCN, SiN or SiO₂, are deposited using, forexample, PECVD, HARP or HDP techniques, on the isolation regions 115,silicide layers 140, layer 105 and on the stacked structures includingthe fins 120 and the hardmasks 125. In addition, a dielectric material,including, but not limited to silicon dioxide (SiO₂), low-temperatureoxide (LTO), high-temperature oxide (HTO), field oxide (FOX) or someother dielectric, is deposited to form interlayer dielectric layers 215.The interlayer dielectric layers 215 can be deposited using depositiontechniques including, but not limited to, CVD, PECVD, RFCVD, PVD, ALD,MLD, MBD, PLD, and/or LSMCD, sputtering, and/or plating. Planarization,for example, CMP can be performed to remove excess material from layers150 and 215 and planarize the resulting structure.

FIG. 9 is a cross-sectional view illustrating removal of portions ofspacer dielectric layers in a method for manufacturing a semiconductordevice, according to an exemplary embodiment of the present invention.As shown in FIG. 9, portions of the spacer dielectric layers 150 areremoved by, for example, an etchback process, to bring the spacer layers150 down to correspond to lower portions of the fins 120 and lowersurfaces of the interlayer dielectric layers 215. Then, as shown in FIG.10, the interlayer dielectric layers 215 are removed using, for example,a selective etching process. The spacer layers 150 cover the top andside portions of the silicide layer 140 so that the silicide layer 140is encapsulated by the spacer layers 150.

In an alternative process for forming spacer layers following from FIG.6, FIG. 11 is a cross-sectional view illustrating deposition ofdielectric layers in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention. As shownin FIG. 11, spacer dielectric layers 250, such as, for example aPECVD-type, HARP-type or HDP-type low-K dielectric layers, including,but not limited to, SiBCN, SiOCN, SiN or SiO₂, are deposited using, forexample, PECVD, HARP or HDP techniques, on the isolation regions 115,silicide layers 140, layer 105 and on the stacked structures includingthe fins 120 and the hardmasks 125. As can be seen in FIG. 11, thedielectric layers 250 are deposited to be thicker on horizontal portions(e.g., on the isolation regions 115, silicide layers 140, layer 105, andon the top surfaces of the hardmasks 125) than on the vertical sideportions of the stacked structures including the fins 120 and thehardmasks 125.

Then, referring to FIG. 12, an anisotropic etching process, such as ME,ion beam etching, plasma etching or laser ablation is performed tocompletely remove the dielectric layers 250 from the vertical sideportions of the stacked structures including the fins 120 and thehardmasks 125, while leaving part or all of the dielectric layers on thehorizontal portions. The spacer layers 250 cover the top and sideportions of the silicide layer 140 so that the silicide layer 140 isencapsulated by the spacer layers 250.

The following FIGS. 13-27 flow from FIG. 12 as can be seen by thepresence of the spacer layers 250 on top surfaces of the hardmasks 125.However, it is to be understood that substantially the same processsteps as those described in connection with FIGS. 13-27 can also flowfrom FIG. 10.

FIG. 13 is a cross-sectional view illustrating deposition of a gatestructure in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention. As shownin FIG. 13, a high-K dielectric layer 160 including but not limited to,HfO₂ (hafnium oxide), ZrO₂ (zirconium dioxide), hafnium zirconium oxideAl₂O₃ (aluminum oxide), and Ta₂O₅ (tantalum pentoxide) is deposited onthe spacer layers 250 and on and around the stacked structures includingthe fins 120, hardmasks 125 and spacer layers 250. A work-function metal(WFM) layer 165, including but not limited to, for a pFET, titaniumnitride (TiN), tantalum nitride (TaN) or ruthenium (Ru), and for annFET, TiN, titanium aluminum nitride (TiAlN), titanium aluminum carbonnitride (TiAlCN), titanium aluminum carbide (TiAlC), tantalum aluminumcarbide (TaAlC), tantalum aluminum carbon nitride (TaAlCN) or lanthanum(La) doped TiN, TaN, is deposited on the high-K dielectric layer 160,and a gate layer 170 including, but not limited to amorphous silicon(a-Si), or metals, such as, for example, tungsten, cobalt, zirconium,tantalum, titanium, aluminum, ruthenium, copper, metal carbides, metalnitrides, transition metal aluminides, tantalum carbide, titaniumcarbide, tantalum magnesium carbide, or combinations thereof isdeposited on the WFM layer 165. The gate structure including the high-Kdielectric layer 160, WFM layer 165 and gate layer 170 may be formedusing, for example, deposition techniques including, but not limited to,CVD, PECVD, RFCVD, PVD, ALD, MLD, MBD, PLD, and/or LSMCD, sputtering,and/or plating.

FIG. 14 is a cross-sectional view illustrating removal of part of thegate structure in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention. As shownin FIG. 14, a planarization process, such as, for example, CMP, isperformed to remove an upper portions of the high-K dielectric layer160, WFM layer 165 and gate layer 170. FIG. 14 illustrates that theplanarization is performed down to the spacer layers 250. Alternatively,the planarization can be performed down to the hardmasks 125, resultingin removal of the spacer layers 250.

FIG. 15 is a cross-sectional view illustrating formation of a mask forgate structure patterning, and FIG. 16 is a cross-sectional viewillustrating gate structure patterning in a method for manufacturing asemiconductor device, according to an exemplary embodiment of thepresent invention. As shown in FIGS. 15 and 16, a mask 180, such as, forexample, a gate mask to pattern the gate is deposited on the planarizedgate structure to cover portions of the gate structure that will remainafter a removal process. The removal process can include, but is notlimited to, a lithography process (e.g., optical or extreme ultraviolet(EUV) direct patterning or a spacer imaging transfer process). Usingoptical lithography as an example, an organic planarization layer (OPL),silicon-containing antireflection coating (SiARC) and photoresist areformed on the planarized gate structure, then after exposure anddevelopment, the photoresist will be formed into patterns. Then, thephotoresist will be used as mask when etching the SiARC. After that, thepatterned SiARC becomes a hard mask to pattern the OPL. Finally thepatterned OPL is used as mask 180 when etching down the gate material.As a result, the lithography pattern is transferred to form the gatematerial. As shown in FIG. 16, the etching process, including but notlimited to, fluorinated gases, such as carbon tetrafluoride (CF₄),sulfur hexafluoride (SF₆) or fluoroform (CHF₃), is then performed toremove those portions of the gate structure left exposed by the mask 180where gates are not required.

FIG. 17 is a cross-sectional view illustrating deposition of dielectriclayers to encapsulate the remaining gate structure in a method formanufacturing a semiconductor device, according to an exemplaryembodiment of the present invention. As shown in FIG. 17, the mask 180is stripped using, for example, using, for example, an N₂ or O₂ plasmaashing process or H₄SO₄/H₂O₂/H₂O mixed solution. Dielectric layers 225are deposited using, for example, ALD or MLD, on sides of the remaininggate structure, and on spacer layers 250. The dielectric layers 225 caninclude, but are not limited to, SiN, SiBCN or SiO₂.

In addition, a dielectric material, including, but not limited to SiO₂,LTO, HTO, FOX or some other dielectric, is deposited to form interlayerdielectric layers 315 adjacent the dielectric layers 225. The interlayerdielectric layers 315 can be deposited using deposition techniquesincluding, but not limited to, CVD, PECVD, RFCVD, PVD, ALD, MLD, MBD,PLD, and/or LSMCD, sputtering, and/or plating. Planarization, forexample, CMP can be performed to remove excess material from layers 225and 315 and planarize the resulting structure.

FIG. 18 is a cross-sectional view illustrating gate structure recessingin a method for manufacturing a semiconductor device, according to anexemplary embodiment of the present invention. As shown in FIG. 18,portions of the encapsulated gate structure between the dielectriclayers 225, including the high-K dielectric layers 160, WFM layers 165and gate layers 170, are removed using, for example, an anisotropic etchprocess, such as ME, ion beam etching, plasma etching or laser ablation.As can be seen, the layers 160, 165 and 170 are recessed to lowerheights above the substrate 102.

FIG. 19 is a cross-sectional view illustrating deposition of dielectricspacer layers in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention. As shownin FIG. 19, spacer dielectric layers 350, such as, for example aPECVD-type, HARP-type or HDP-type low-K dielectric layers, including,but not limited to, SiBCN, SiN or SiO₂ are deposited using, for example,PECVD, HARP or HDP techniques, on the recessed gate structures,dielectric layers 225 and 315, and on the stacked structures includingthe fins 120, hardmasks 125 and layer 250 (if layer 250 remained fromthe planarization step in FIG. 14). As can be seen in FIG. 19, thedielectric layers 350 are deposited to be thicker on horizontal portions(e.g., on the recessed gate structures, top surfaces of dielectriclayers 225 and 315, and on top surfaces of the stacked structures) thanon the vertical side portions of the stacked structures.

Then, referring to FIG. 20, an anisotropic etching process, such as ME,ion beam etching, plasma etching or laser ablation is performed tocompletely remove the dielectric layers 350 from the vertical sideportions of the stacked structures, while leaving part or all of thedielectric layers on the horizontal portions.

FIG. 21 is a cross-sectional view illustrating deposition of interlayerdielectric layers in a method for manufacturing a semiconductor device,according to an exemplary embodiment of the present invention. As shownin FIG. 21, a dielectric material, including, but not limited to SiO₂,LTO, HTO, FOX or some other dielectric, is deposited to form interlayerdielectric layers 415 on the recessed gate structures, including theremaining horizontal portions of layer 350 on top surfaces of therecessed gate structures. The interlayer dielectric layers 415 can bedeposited using deposition techniques including, but not limited to,CVD, PECVD, RFCVD, PVD, ALD, MLD, MBD, PLD, and/or LSMCD, sputtering,and/or plating. Planarization, for example, CMP can be performed toremove excess material from layers 415 and planarize the resultingstructure. As shown in FIG. 22, the planarization can be performed downto the hardmasks 125 on the fins 120.

FIG. 23 is a cross-sectional view illustrating selective removal of thehardmask and portions of the dielectric layers in a method formanufacturing a semiconductor device, according to an exemplaryembodiment of the present invention. As shown in FIG. 23, the hardmaskand portions of the dielectric layers 125, 225 are selectively removed,using for example, a selective etch process. The selective etch processcan include, for example, fluorinated gas (such as SF₆, CH₄, or CHF₃)based dry etching or hot phosphoric acid (H₃PO₄) etching. According toan embodiment, the hardmask and dielectric layers 125, 225 include thesame or similar material so that these layers 125, 225 can beselectively etched with respect to the other structures. As can be seen,the layers 125, 225 are etched until the hardmasks 125 are removed sothat the remaining portions of the dielectric layers 225 each have a topsurface that is level or substantially with a top surface of the fins120. Then, as shown in FIG. 24, the portions of the interlayerdielectric layers 315, 415 protruding above the top surfaces of thedielectric layers 225 and the fins 120 are removed using, for example,another selective etching process, such as a selective oxide etch using,for example, F/NH₃ based dry etching. According to an embodiment, theinterlayer dielectric layers 315, 415 include the same or similarmaterial so that these layers 315, 415 can be selectively etched withrespect to the other structures.

FIG. 25 is a cross-sectional view illustrating epitaxial growth of topsource/drain regions in a method for manufacturing a semiconductordevice, according to an exemplary embodiment of the present invention.As shown in FIG. 25, top source/drain regions 190 are epitaxially grownon the fins 120. Application of the sources for nFET and pFET epitaxialgrowth can be done by using block level patterning. For an nFET, As or Pdoped Si or SiC source/drain regions 190 are epitaxially grown. For apFET, B doped SiGe or Si source/drain regions 190 are epitaxially grown.Doping can be at concentrations in the general range of e20/cm³. As canbe seen in FIG. 25, epitaxial growth is stopped prior to merging so thatthe epitaxial regions 190 are not merged with each other. Alternatively,the epitaxial growth is not stopped prior to merging so that theepitaxial regions 190 are merged with each other. While the shape of theepitaxial source/drain regions 190 is illustrated as pentagonal, theembodiments of the present invention are not necessarily limitedthereto, and other epitaxial shapes may be formed depending onorientations and materials used.

FIG. 26 is a cross-sectional view illustrating deposition of aninterlayer dielectric layer in a method for manufacturing asemiconductor device, according to an exemplary embodiment of thepresent invention. As shown in FIG. 26, a dielectric material,including, but not limited to SiO₂, LTO, HTO, FOX or some otherdielectric, is deposited on the structure from FIG. 25 on and around thetop source/drain regions 190 to form interlayer dielectric layer 515.The interlayer dielectric layer 515 can be deposited using depositiontechniques including, but not limited to, CVD, PECVD, RFCVD, PVD, ALD,MLD, MBD, PLD, and/or LSMCD, sputtering, and/or plating. Planarization,for example, CMP can be performed to remove excess material from layers515 and planarize the resulting structure.

FIG. 27 is a cross-sectional view illustrating formation of contactregions in a method for manufacturing a semiconductor device, accordingto an exemplary embodiment of the present invention. As shown in FIG.27, contact regions 201 and 203 (e.g., middle of the line (MOL) contactregions) are formed by etching vias in the interlayer dielectric layers315 and/or 515, and filling the vias with an electrically conductivematerial. For example, contact region 201 is formed by etching a via ininterlayer dielectric layer 515 and filling the via with a conductivemetal. Similarly, contact region 203 is formed by etching a via throughinterlayer dielectric layers 315, 515 and spacer layer 250 down to thesilicide layer 140, and filling the via with a conductive metal. As canbe seen, the contact region 203 contacts the silicide layer 140 toprovide electrical current to the bottom source/drain region 105.

The conductive metal can include, but is not limited to, tungsten,cobalt, ruthenium, copper, or combinations thereof, and may be depositedusing, for example, deposition techniques including, but not limited to,CVD, PECVD, RFCVD, PVD, ALD, MLD, MBD, pulsed laser deposition, and/orLSMCD, sputtering, and/or plating. Planarization, for example, CMP canbe performed to remove excess contact material after deposition andplanarize the resulting structure.

Although illustrative embodiments of the present invention have beendescribed herein with reference to the accompanying drawings, it is tobe understood that the invention is not limited to those preciseembodiments, and that various other changes and modifications may bemade by one skilled in the art without departing from the scope orspirit of the invention.

We claim:
 1. A method for manufacturing a semiconductor device,comprising: forming a source/drain region on a semiconductor substrate;forming a semiconductor layer on the source/drain region; patterning thesemiconductor layer into a plurality of fins extending from thesource/drain region vertically with respect to the semiconductorsubstrate, wherein the source/drain region is located under bottom endsof the plurality of fins; forming a silicide layer on exposed portionsof the source/drain region; forming an electrically conductive contacton the silicide layer; and forming a spacer layer on the silicide layer,wherein the electrically conductive contact extends through an openingin the spacer layer to contact the silicide layer; wherein thesemiconductor device comprises a vertical field-effect transistor (FET)device configured to carry current through the plurality of fins in adirection perpendicular to a top surface of the semiconductor substrateon which the source/drain region is formed and from which the pluralityfins vertically extend.
 2. The method according to claim 1, wherein thesilicide layer wraps around an edge of the source/drain region.
 3. Themethod according to claim 1, further comprising forming a protectivelayer on the plurality of fins prior to forming the silicide layer onthe exposed portions of the source/drain region.
 4. The method accordingto claim 1, further comprising: removing a portion of the source/drainregion and a portion of the substrate under the source/drain region toform a trench; and filling the trench with a dielectric material to forman isolation region.
 5. The method according to claim 4, furthercomprising recessing the isolation region to expose an edge of thesource/drain region prior to forming the silicide layer on the exposedportions of the source/drain region.
 6. The method according to claim 1,further comprising: forming a gate structure on the spacer layer and onthe plurality of fins; and patterning the gate structure to remove aportion of the gate structure to expose a portion of the spacer layerwhere the opening through which the electrically conductive contactextends will be formed.
 7. The method according to claim 6, furthercomprising recessing the gate structure between the plurality of fins.8. The method according to claim 7, further comprising forming anotherspacer layer on the recessed gate structure.
 9. The method according toclaim 1, wherein the spacer layer comprises at least one of an oxide,silicon nitride (SiN), siliconborocarbonitride (SiBCN), and siliconoxycarbonitride (SiOCN).
 10. The method according to claim 1, furthercomprising forming another source/drain region on top ends of each ofthe plurality of fins.
 11. The method according to claim 10, forming agate structure over the silicide layer and between the plurality offins, wherein the gate structure is positioned under the othersource/drain region.
 12. A method for manufacturing a semiconductordevice, comprising: forming a first active region on a semiconductorsubstrate; forming a semiconductor layer on the first active region;patterning the semiconductor layer into a plurality of fins extendingfrom the first active region vertically with respect to thesemiconductor substrate, wherein the first active region is locatedunder bottom ends of the plurality of fins; forming a silicide layer onexposed portions of the first active region; forming an electricallyconductive contact on the silicide layer; forming a second active regionon top ends of each of the plurality of fins; forming a gate structurebetween the plurality of fins, wherein the gate structure is positionedover the first active region and under the second active region; andforming a spacer layer on the silicide layer, wherein the electricallyconductive contact extends through an opening in the spacer layer tocontact the silicide layer; wherein the semiconductor device comprises avertical field-effect transistor (FET) device configured to carrycurrent through the plurality of fins in a direction perpendicular to atop surface of the semiconductor substrate on which the first activeregion is formed and from which the plurality fins vertically extend.13. The method according to claim 12, wherein the silicide layer wrapsaround an edge of the first active region.
 14. The method according toclaim 12, further comprising forming a protective layer on the pluralityof fins prior to forming the silicide layer on the exposed portions ofthe first active region.
 15. The method according to claim 12, furthercomprising: removing a portion of the first active region and a portionof the substrate under the first active region to form a trench; andfilling the trench with a dielectric material to form an isolationregion.
 16. The method according to claim 15, further comprisingrecessing the isolation region to expose an edge of the first activeregion prior to forming the silicide layer on the exposed portions ofthe first active region.
 17. The method according to claim 12, whereinthe gate structure is formed on the spacer layer, and the method furthercomprises patterning the gate structure to remove a portion of the gatestructure to expose a portion of the spacer layer where the openingthrough which the electrically conductive contact extends will beformed.
 18. The method according to claim 17, further comprisingrecessing the gate structure between the plurality of fins.